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Masanori Konda, Hiroshi Ichikawa, Hiroyuki Tomita, and Meghan F. Cronin

north–south contrast of the ocean surface structure can affect the modification of the air mass through changes in the exchange of heat, moisture, and momentum. The large heat flux in the KE region is correlated with the basin-scale air–sea coupling systems such as the Pacific decadal oscillation (PDO) and other subsequent modes ( Mantua et al. 1997 ; Bond et al. 2003 ; Kwon and Deser 2007 ; Di Lorenzo et al. 2008 ). Previous studies have pointed out that the atmospheric circulation field

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Jeffrey Shaman, R. M. Samelson, and Eric Skyllingstad

1. Introduction The largest wintertime heat fluxes from the ocean to the atmosphere in the North Atlantic occur in the region of the Gulf Stream extension and the adjacent waters of the northwestern portion of the subtropical gyre ( Esbensen and Kushnir 1981 ; Josey et al. 1999 ). These heat fluxes are supported in the ocean by advective heat convergence in the Gulf Stream and by seasonal heat storage in the surrounding waters, especially the subtropical mode water to the south and east of the

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Masami Nonaka, Hisashi Nakamura, Bunmei Taguchi, Nobumasa Komori, Akira Kuwano-Yoshida, and Koutarou Takaya

overlying atmosphere is still under debate. Summarizing the results of numerical experiments carried out previously with atmospheric general circulation models (GCMs), Kushnir et al. (2002) concluded that no coherent large-scale atmospheric response had been obtained to prescribed midlatitude sea surface temperature (SST) anomalies. Rather, midlatitude SST anomalies in general have been shown to be forced primarily by atmospheric anomalies ( Frankignoul 1985 ) through changes in surface heat fluxes

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Mototaka Nakamura and Shozo Yamane

) composite anomalies in the monthly-mean circulation and high-frequency transients in the atmosphere to obtain a typical atmospheric state that accompanies the patterns of anomalous B , (iii) composite SSTA to obtain a typical oceanic state that accompanies and precedes the patterns of anomalous B , and (iv) composite anomalous net surface heat flux that accompanies and precedes the pattern of anomalous B . With this approach, we obtain typical pictures of anomalous states in the atmosphere and oceans

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Young-Oh Kwon, Michael A. Alexander, Nicholas A. Bond, Claude Frankignoul, Hisashi Nakamura, Bo Qiu, and Lu Anne Thompson

1. Introduction Atmosphere–ocean interactions are exceptionally strong over western boundary currents and their eastward extensions (hereafter collectively WBCs): for example, the largest mean and variance at interannual and longer time scales of the net surface heat flux (Q net ) over the global ocean occurs in WBC regions ( Wallace and Hobbs 2006 ). Poleward heat transports by the ocean and atmosphere are comparable in the tropics, until the ocean transfers ~70% of its heat transport to the

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Nicholas A. Bond, Meghan F. Cronin, and Matthew Garvert

et al. 2006 ; Minobe et al. 2008 ; Tokinaga et al. 2009 ), the extent to which the larger-scale atmospheric circulation is sensitive to anomalies in SST is controversial (e.g., Kushnir et al. 2002 ). There is tentative evidence that this sensitivity is mediated by the atmosphere’s basic state (e.g., Peng et al. 1997 ; Bond and Harrison 2000 ). It is plausible to suppose that extratropical transitions are particularly sensitive to SST, because of the latter’s impact on the surface fluxes of

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James F. Booth, Lu Anne Thompson, Jérôme Patoux, Kathryn A. Kelly, and Suzanne Dickinson

influences the transient dynamics of the atmosphere. Nakamura et al. (2008) use an AGCM to show that the SST front in the Southern Hemisphere acts to anchor, or fix the location of, the wintertime storm track. They theorize that the turbulent heat fluxes from the ocean to the atmosphere on the warm side of the SST front reinvigorate the low-level atmospheric baroclinicity that is removed by wind advection associated with a passing storm. Nakamura and Yamane (2009) show that anomalies in the monthly

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Xujing Jia Davis, Lewis M. Rothstein, William K. Dewar, and Dimitris Menemenlis

exist: seasonal and interannual. The seasonal cycle of model NPSTMW formation, isolation, and dissipation is described in detail. The interannual regime of model NPSTMW variability is shown to be closely tied to the phase change of the Pacific decadal oscillation (PDO) index. This connection is more clearly seen through an analysis of interannual changes in basin-wide wind stress and surface heat flux. 2. Model description This study is based on a global ocean simulation made available by the

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Bunmei Taguchi, Hisashi Nakamura, Masami Nonaka, and Shang-Ping Xie

these oceanic processes rather than by local atmospheric forcing, those SST anomalies in the KOE region accompany surface turbulent heat fluxes that can act as a thermal forcing on the overlying atmosphere ( Tanimoto et al. 2003 ; Nonaka et al. 2006 ). In fact, numerical experiments by Peng and Whitaker (1999) suggest that the SST anomaly in the KOE region may be able to force a basin-scale atmospheric response, although it may be sensitive to the background flow. Furthermore, observational

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Terrence M. Joyce, Young-Oh Kwon, and Lisan Yu

particularly identify the dynamical cause. Because the system is coupled, there are processes within the atmosphere and the ocean separately that will force an alignment between the two ( Hoskins and Valdes 1990 , Nakamura et al. 2008 ): storms can produce vorticity fluxes that enhance the midlatitude zonal jet, which can affect the location of the GS and KE, and then further influence the development of the storms. Recently Tanimoto et al. (2003) have examined decadal variability in SST and interannual

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